In the past, in order to obtain high projectile velocities in the range of three (3) to ten (10) kilometers/second prior art devices have had to use two stage light gas guns. These gas guns had to rely on heavy pistons being propelled by a propellant charge, often using a conventional solid propellant, into a pump tube containing light gas. The light gas was compressed to extremely high pressures and high energy levels which, in turn, expanded against a projectile in the launch tube. The problem with this prior art device was requirement of an extremely long and heavy pump tube, up to 20 meters in length, and high accelerations to 250,000 G's.
Prior art single stage light gas guns with velocities in the 2-3 km/sec. range obtain these velocities by igniting a mixture of hydrogen and oxygen in a hydrogen rich mixture. The resulting gas is much heavier than hydrogen because of the large amounts of water in the mixture. This results in much lower projectile velocities than would be obtainable from a pure hydrogen light gas gun. The prior art single stage gas guns were not able to obtain the high projectile energy which resulted from the high compression of the two stage guns.
Alternate configurations of the two stage gas gun which produced shorter and lighter weight guns fail in obtaining the necessary velocity because they cannot bring the light gas to high enough pressure and energy levels.
None of the prior art two stage guns use expanded hydrogen as an energy source for a traveling charge, and none of the prior art single stage gas guns use pure hydrogen.